ᐅ Identifying the Quality of Basement Finishing

Hello everyone,

We moved into a house built in 1980 about a year ago. One basement room was converted into a "living space" around 10 years ago by the previous owner. It has relatively bright windows and heating. I’m now considering setting up my office there because the attic is simply too warm (despite new insulation).

I don’t know how or by whom the conversion was done back then, but it was probably by professionals, not the previous owner. The ceiling has a wooden cladding, the floor also has a layered construction, and two exterior walls have a classic wooden paneling with polystyrene insulation behind it. I opened a spot once to check, and everything looked dry and clean. Behind the wood comes directly the polystyrene (4cm (1.5 inches)) and then the wall itself. So here are my questions for you:
1) Is it acceptable to use wood plus polystyrene (and nothing else) on an exterior wall like this?
2) Is this also appropriate for the floor? (I haven’t checked yet, but there is a 2cm (0.8 inch) build-up there as mentioned)
3) Generally, should you only worry if the wall gets wet from outside and/or if the indoor humidity is too high? (The humidity is always below 70%, usually just above 60%, no matter how I ventilate – and one wall can’t get rain on it because of the roof and terrace above)

The room is fine overall – there was just a bit of mold on the outside of the wooden paneling at one spot when I had a cabinet pushed right up against it for several weeks. Otherwise, no moisture issues.

Thanks for your assessment!
Best regards,
Peter

Internal insulation is not a problem in itself, but it should not allow air to flow behind it. Placing furniture directly against exterior walls is also not ideal, as you have noticed, because it restricts air circulation. Radiant heat cannot easily reach behind the furniture, and the exterior wall absorbs the heat from the air in the gap, which can lead to moisture accumulation. It is better to leave a 10cm (4 inches) gap or avoid placing furniture directly against exterior walls. Alternatively, place the furniture so close to the wall that air cannot flow behind it. If no warm, moist indoor air can enter any gaps, then condensation on cooler surfaces cannot occur.

A 2cm (0.8 inches) floor insulation is quite thin for a heated room above soil. During our renovation, we had to install 10cm (4 inches) of insulation (6cm (2.4 inches) of which had a thermal conductivity of 0.022 W/(m·K)) to meet the minimum requirements of the 2009 Energy Saving Ordinance.

The room seems to have been completely fine for several years. There was once a mold problem that was caused by user error but has since disappeared.

Are you trying to determine if the condition of the room as it is now is acceptable?
In my opinion, you should just use the room. It doesn’t seem like there are any ongoing issues.
If it gets too cold in winter, you can consider adding more insulation, but if not, then everything should be fine.

As long as everything remains dry as described and no mold is visible (including no musty smell), I wouldn’t worry about it at all.

Hello to both of you, and thank you for your responses.
Yes, my main concern is whether what was done is acceptable. The topic seemed to fit best under "building defects" because I am not sure if this could cause a problem or not.

I recently read online that you should never use expanded polystyrene (EPS) on exterior walls. As I mentioned, it looks neat, but there is only wooden cladding plus the EPS and nothing else. The EPS is placed directly against the wall.
- Could this work, or is it almost always problematic?

(By the way, the floor has a thickness of 4 cm (1.6 inches), but I still need to check what material it is.)

Whether this is standard practice or "botched" work, I cannot assess. However, if everything is fine, I would not be too concerned about it in the end.